What rights are reserved?

The short version: Not many. I'm quite lenient about copyright.

If I've made art of your character:
You have full display rights -- post it anywhere, on anything, with anybody.
You have full reproduction and distribution rights -- print a poster, put it on a T-shirt, study it in class.
You have full sales rights -- if you do print a poster or make a T-shirt, you can sell it.
You have full rights to make derivative works -- paint over it, put it in a game, use it in a modern art installation.
Just say "Echovita made this" (or something to that effect), and you're A-OK. :-)

People with these rights will be labeled under the box in the Gallery. For everyone except the recipient (that means you, person who hasn't gotten art of your character), the art is subject to the character owner's wishes. For "On-missions," I give the recipient the option to release the work as CC-BY 4.0, CC-BY-SA 4.0, CC-BY-ND-NC 4.0, or All Rights Reserved. In layman's terms, those translate roughly to:

: Do whatever, just give credit.
: Do whatever, give credit, and license derivative works with the same license.
: Give credit if you post it or use it, but don't make money from it or make derivative works with it.
: Do not post, do not pass GO, do not collect $200.

The license type will be visible on a piece's Gallery page. (If it doesn't have a Gallery page, you can safely assume it's All Rights Reserved.)

Art of my own characters is typically licensed under CC-BY 4.0.
Check the Gallery page to make sure it's not an outlier, but in general...
Print it. Post it. Wear it. Share it. Just give credit where it's due.

Keep the Echovita/EQP signature in place or leave attribution somewhere visible, and you're good to go. Have fun. :-)

The characters themselves are All Rights Reserved, but you have my permission to draw them (with some reasonable limitations.)
See the Characters page for full details.
The short version: Don't draw NSFW works, lewdity, "ship" art, or anything out of character. I can't stop your pen -- but I'd rather not see those things on the 'net.

As for the site:
I have enough friends in CompSci who will attest that any written code is effecively public domain. Who am I to tell them any different?
All code for the webpages is licensed under CC0. It's pretty janky, but if you want to borrow it, go ahead. (Or, just get a copy of Dreamweaver 2 and build better code yourself.)
All Lonewall articles have licensing clearly labeled. Most are CC-BY-4.0.
All other text (e.g. this page, the big list of links, and the numerous attempts at humor) is All Rights Reserved.